Semi-automatic firearms, such as rifles and shotguns, are designed to fire a round of ammunition, such as a cartridge or shotshell, in response to each squeeze of the trigger of the firearm, and thereafter automatically load the next shell or cartridge from the firearm magazine into the chamber of the firearm. During firing, the primer of the round of ammunition ignites the propellant (powder) inside the round, producing an expanding column of high pressure gases within the chamber and barrel of the firearm. The force of this expanding gas propels the bullet/shot of the cartridge or shell down the barrel.
In semi-automatic rifles and shotguns, and in particular in gas operated firearms, a portion of the expanding gases from firing typically are directed through a duct or port that interconnects the barrel of the firearm to a piston assembly that generally houses an axially moveable piston, which interacts with the bolt assembly of the firearm to cause cycling of the bolt assembly.
During a firing operation, a portion of the expanding combustion gases from the barrel is directed into the gas block of the gas operating system, the gas flow contacting and driving the gas piston rearwardly. This rearward action of the gas piston, which in turn is translated to the bolt, functions to cause a spent cartridge/shell casing to be automatically cleared or ejected from the chamber, a new round to be loaded into the chamber, and the hammer to be recocked for a next firing cycle. The gases directed into the gas block generally result from combustion of the primer and propellant powder of the round upon firing of the round.
Known gas actuating piston assemblies for semi-automatic firearms can suffer from numerous disadvantages, including the inability to regulate the gas energy being transmitted to the piston. For example, when lower power cartridges or shells are used, the pressure of the discharge gases sometimes is not sufficient to properly or fully actuate/drive the piston assembly, which can result in failure to fully cycle the action or jammed shells or cartridges.